This invention concerns a new and improved one-piece, integral card guide unit for use in guiding and supporting circuit boards in a circuit board card cage. Circuit board card cages are well known. The general structure of such a card cage is shown and described and the publication VME Bus Specification Manual, Rev. c.1, October 1995, pages 215-247 of this publication by Motorola entitled "Series in Solid-State Electronics Rev. c.1; which publication is also entitled "The VME Bus Specification" dated October 1995. This VME Bus Specification Manual also is known as the "IEC 821 Bus" and the "IEEE P1014/d1.2," and was printed by Printex Publishing, Inc.
Such circuit board card cages generally comprise enclosures having side walls and a back plane, secured together in a frame that comprises elongated front and rear cross members connected to the upper surface of the side walls and back plane and to the lower surface of the side walls and back plane, to form the circuit card rack enclosure. This enclosure is often open in the front, top and the bottom to allow air circulation around the individual circuit boards to cool the electronic components. The top and bottom and front openings can be closed if desired.
Positioned within the card cage structure are card rails or guides that extend generally between the front and rear cross members. These card guides have grooves that are opposing between the lower and upper card guide rails, for receiving the edges of the circuit boards. The card guides are also laterally spaced from each other, to provide space between the electrical and electronic components secured to the circuit boards. At the end of the known circuit boards, there is an electrical connection that interconnects with an electrical connection on the rear panel, known as the back plane electrical connector. The card rails in these card cages are often individually located and secured to the front and rear cross members in a manner to provide a vertical orientation of the circuit board to align the electrical connection on the circuit board with the electrical receptacle on the back plane. Here, problems arise in that the card rails often become skewed, moved or twisted by vibration or in the general use of the card cage, which can include shocks received by the card cage or just the overall use of the card cage in the environment in which the card cage is located. Such occurrences cause the circuit board to become misaligned to the extent that a good easy straight forward and precise connection cannot be made to the electrical circuit on the back plane. Further, in many card cages, the structure of the card rails and indeed the card cage in general is made of light sheet metal type construction or of plastic or other suitable materials. In these assemblies, there is a weak or insufficient connection between the card rails and the cross support members that will prevent slight movements or skewing of some of the card rails relative to other card rails which skews the position of the circuit boards. There are also some card guides units that are connected to the cross members in a manner where it is possible for the card guides to move relative to the cross member. This skews the circuit board in the guide relative to the opposing card guide, which again has an adverse effect on the circuit board being able to make the correct electrical connection.
So, there is a definite need for a new and improved circuit board card guide rail in which the card guide bars are integral with the multiple cross members, so that identical card rack guide units are connectable to the side walls and back plane of the card cage. This provides precise alignment of the circuit board with the back plane electrical connections, is not subject to twisting and other movements between the card guides and the cross members, and which card guides are formed in a manner that allows some transitory tolerance to twisting, vibration and other shocks to the card cage, while still maintaining permanent, precise alignment of the circuit board with the back plane electrical connections.